Temperature independent uranium alloy electrical resistor



March 1961 M. BLEIBERG ETAL 2,977,557

TEMPERATURE INDEPENDENT URANIUM ALLOY ELECTRICAL RESISTOR Filed April 12, 1957 2 Sheets-Sheet 1 159/: MO, 85 U l IOO oomw 8 3 mm E9; cozogmo Emuhmm Temperature C 5% 3 U 3% Mo 91%u sbo Temperature C I50 Temperature Kelvin Fig.2.

WITNESSES INVENTORS Melvin L. Bleiberg 8 Eber K.HOHernon.

BY J fiz ATTOR Y 4% Z -wr mama/W 7W March 28, 1961 M. BLEIBERG ETAL 2,977,557

TEMPERATURE INDEPENDENT URANIUM ALLOY ELECTRICAL RESISTOR 2 Sheets-Sheet 2 Filed April 12, 1957 13% Mo,87/ U |O.6 Mo, 89.4 u

I50 200 Temperu'rure- Kelvin Fig.4.

Fig.5.

TEMPERATURE INDEPENDENT URANIUM ALLOY ELECTRICAL RESISTOR Melvin L. Bleiberg, Mount Lebanon, and Eber K. Halteman, Whitehall, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 12, 1957, Ser. No. 652,403

Z CRainrs. (Cl. 338-7) This invention relates to electrical resistors, and particularly to electrical resistors comprising resistance material that exhibits a very small change in electrical resistance over an extremely wide temperature range.

The object of this invention is to provide electrical resistors which comprise an alloy resistance material, uranium and molybdenum or niobium, that has a very small change in electrical resistance over an extremely wide temperature range.

Another object of this invention is to provide members suitable for use as electrical resistances comprising an alloy composed of from 3% to 15% of at least one element selected from the group consisting of molybdenum and niobium and the balance being uranium, said members being characterized by having, over a wide temperature range, a very small change in electrical resistance.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter. For a better understanding of the nature and objects of the invention, reference should be had to the following detailed description and drawing, in which:

Figure l is a graph plotting percent deviation from resistance at 25 C. against temperature for a specific alloy;

Fig. 2 is a graph plotting the ratios of the resistance at C. to the resistance at various temperatures against temperature for several alloys;

Fig. 3 is a graph plotting resistivity of a specific alloy against temperature measured in degrees Kelvin;

Fig. 4 is a graph plotting resistivity of specific alloys against temperature measured in degrees Kelvin; and

Fig. 5 is a view in elevation of an electrical resistor.

In accordance with this invention, it has been found that electrical resistors that are substantially temperature independent can be prepared from members comprising an alloy composed of from 3% to 15% by weight of at least one element selected from the group consisting of molybdenum and niobium and the balance being substantially all uranium.

The resistance members of this invention which are employed in elongated or Wire-like form show very little change in electrical resistance over a wide temperature range. The graph shown in Pig. 1 of the drawing shows the percent of change in resistance with change in temperature for an elongated member comprising an alloy composed of 85% uranium and 15% molybdenum. It will be noted that the change in resistance varies only :0.15% in the temperature range of from 0 C. to 100 C., and only about 0.5% in the temperature range of from 0 C. to 300 C. The percent change in resistance is based on the resistance of the elongated member at 25 C.

The alloys employed in this invention may be prepared by melting the desired amount of uranium with the desired amount of niobium or molybdenum in an induction furnace comprising a graphite crucible coated with a wash of zirconium oxide. The uranium may comprise natural uranium containing not over a few hundredths of 1% of impurities. The uranium may be entirely natural uranium or natural uranium that has been enriched with, for example, 10% of uranium 235. The molten alloy is poured into a graphite crucible to produce an ingot. The cast ingot is hot worked by forging, extrusion, rolling and the like into the desired shape of member. The resistance member of this invention will ordinarily be employed in elongated form such as wires and the like, and the ingot may be heated in a salt bath to a temperature of from 1700" F. to 2100 F. and then extruded in the desired form. In some instances, ingots of improved homogeneity and structure have been secured by employing the original cast ingot as the consumable electrode in an arc furnace. The are furnace may be operated as set forth in application Serial No. 367,524, assigned to the assignee of the present invention by the inventors, Robert B. Gordon and Walter J. Hurford.

The following examples are illustrative of the preparation of alloys for use in this invention:

Example I Into a crucible of an induction furnace there were placed 3 parts by weight of molybdenum and 97 parts by weight of natural uranium having the following impurities:

Element: P.p.m. Carbon 26 to 36. Zirconium 50 maximum. Nitrogen 20 maximum. Iron 40 to 55. Silicon 36 to 46. Nickel 10 to 12. Manganese 5 to 7. Chromium 4 to 6. Magnesium 5 to 5.

Other elements Less than 2.

The alloy after having been melted was then poured into a graphite mold and cast into an ingot of a diameter of 2.4 inches. The ingot was then extruded into a wire having a diameter of about 62 mils. A member 4 inches long was cut from the extruded wire and homogenized by annealing at 900 C. for 24 hours and quenched in water to retain the gamma phase throughout.

Example II The process of Example I was employed to prepare additional members of the following compositions: 5% molybdenum-95% uranium, 7% molybdenum-93% uranium, 9% molybdenum-91% uranium and 15% molybdenum-% uranium.

The electrical resistances of the members of Examples I and II were measured at 0 C. and at various elevated temperatures. The ratios of the resistance at 0 C. to the resistance at various temperatures were determined and this data are plotted in Fig. 2 of the drawing. It will be observed that the resistance ratio varies very little over the temperature range of from about 400 C. to about 900 C.

Alloys comprising alloys of uranium and niobium can be prepared in accordance with the process of Example I by substituting for the molybdenum an equal amount of niobium. Resistance members comprising an alloy composed of from 3% to 15% niobium and the balance being uranium exhibit temperature independent resistances at elevated temperatures similar to resistance members composed of the uranium-molybdenum alloys.

The resistivity of a resistance member comprising an alloy composed of 10% niobium and uranium was measured at several extreme temperatures. The data obtained are plotted in Fig. 3 of the drawing.

Resistivity or specific resistance is defined as the resistance, in ohms, of a conductor one centimeter in length and one square centimeter in cross sectional area. 7 Referring to Fig. 4 of the drawing, there are plotted the data obtained on the low temperature resistivity of several molybdenum-uranium alloy resistance members.

Fig. 5 of the drawing shows an electrical resistor comprising an elongated resistance member 12 of this invention. The resistor 10 comprises a tubular member 14 which may be of ceramic or the like provided with spiral grooves 16 on the outer surface thereof where elongated resistance member 12 may be positioned. In order to provide terminal connections for the resistor, insulating bushings 18 may be provided, being, for example, inserted in openings in the tube itself in any well known manner for accommodating terminal screws 20.

The electrical resistors of this invention are particularly well adapted for use in electrical apparatus that are subjected to Wide and extreme variations in temperature, such for example as strain gauges used in high altitude aircraft and rockets.

It will be understood that the above description and drawing are only exemplary and not in limitation of the invention.

We claim as our invention:

1. An electrical resistor. comprising, in combination,

. 4 7 an insulated base member having applied thereto an elongated resistance member comprising an alloy composed of from 3% to by weight of at least one element selected from the group consisting of molybdenum and niobium and the balance being uranium, said elongated resistance member being characterized by having, over an extremely wide temperature range, a very small change in electrical resistance.

2. An electrical resistor comprising, in combination, an insulating means having applied thereto a resistance member comprising an alloy composed of from 3% to 15% by weight of at least one element selected from the group consisting of molybdenum and niobium and the balance being uranium, said resistance member being characterized by having a very small change in electrical resistance over an extremely wide temperature range.

United States Atomic Energy Commission Report, BMI-72, June 1, 1951. Report entitled The Constitu tion Diagram of Uranium Rich Uranium Molybdenum Alloys." 

1. AN ELECTRICAL RESISTOR COMPRISING, IN COMBINATION, AN INSULATED BASE MEMBER HAVING APPLIED THERETO AN ELONGATED RESISTANCE MEMBER COMPRISING AN ALLOY COMPOSED OF FROM 3% TO 15% BY WEIGHT OF AT LEAST ONE ELEMENT SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM AND NIOBIUM AND THE BALANCE BEING URANIUM, SAID ELONGATED RESISTANCE MEMBER BEING CHARACTERIZED BY HAVING, OVER AN EXTREMELY WIDE TEMPERATURE RANGE, A VERY SMALL CHANGE IN ELECTRICAL RESISTANCE. 